Polyimides are high temperature, amorphous polymers that are finding applications as adhesives and composite matrix resins. At present, no suitable polyimide exists for use as a composite reinforcement fiber or fabric because of the amorphous nature of this polymer class. In order to meet the high tensile strength (HTS) and high modulus (HM) requirements of a reinforcement the polymer must exhibit either crystallinity or a high degree of order which is usually induced by drawing or extruding.
Presently the only suitable reinforcements for high temperature composite systems are glass and graphite fibers. Other HTS and HM systems such as Dupont's Kevlar (or PRD-49) cannot withstand the temperature requirement for processing high temperature matrix resins. A need for a high temperature strength, high modulus polyimide reinforcement exists not only because of its ability to withstand high processing temperatures, but also, because the glass and graphite fibers form weak bonds with the matrix resin. Since many of these matrix resins are polyimides, polyimide fibers should be more compatible and stronger bonds should be formed.